It has long been recognized that cottonseeds are a valuable source of natural food oil and protein. However, while commercial processes have been developed for extracting oil from cottonseeds, the potential protein value of the seeds has not heretofore been able to be fully realized. This is primarily due to the presence in glanded cottonseed of gossypol, a complex polyphenolic compound which is quite toxic and, therefore, cannot be tolerated in the food of most animals (essentially not at all in human food). Gossypol has even been found to possess some characteristics which make it a natural contraceptive.
To effectively utilize the natural food protein values of glanded cottonseed, therefore, the gossypol present in the seed must first either be extracted destroyed or detoxified. Development of commercially practicable extraction procedures has been hindered due to the fact that gossypol and its derivatives are insoluble in water and most organic solvents. Thus, the gossypol remains in the proteinaceous press cake material from which the food oils have been extracted, usually with hexane. Procedures have been developed for the extraction of gossypol from glanded cottonseed meal, usually involving the use of acetone, but they are relatively time-consuming and expensive.
Attempts at detoxification of gossypol in cottonseed meal from glanded cottonseeds have involved heating the cottonseed meal to split the gossypol ring structure, causing the gossypol to bind with the amino acids present in the protein of the cottonseed meal. In order to destroy gossypol, the procedures thus far developed have required the use of high temperatures (in excess of 150.degree. C.) and pressures, or treatment with ammonia gas. While successful, they have not been widely used commercially. This is because they tend to destroy some protein, thereby substantially decreasing food value of the material. More importantly, detoxification processes develop an "off-flavor" in the product, making it impossible to use the product as a human food or food supple- ment.
Accordingly, present efforts at utilizing the protein value of glanded cottonseed are limited to use of limited quantities of cottonseed meal as an additive to feeds of ruminants (who possess micro-organisms in their first stomach which apparantly detoxify a limited amount of gossypol). Research and development efforts aimed at realizing the protein potential in glanded cottonseed meal as a source of protein for human consumption have mainly been aimed at solvent extraction procedures for removing gossypol from the meal without affecting the protein value.